VHS Horizontal Lines: ReplaceFrameAvg()

AviUser · 29th October 2013, 03:01

Hello,

[Similar topic with no solution]
So I have a video sourced from VHS tape recorded in a TV studio. Every minute or so, for 1-5 frames, horizontal white lines appear on the clip and distort the image in those places.
What I have been doing is DeleteFrame() on each of these, until I realized that this does not sync audio, so I defined:

Code:

function DeleteFrame2(clip clp, int framenumber) {
    return clp.trim(0,framenumber-1) + clp.trim(framenumber+1,0)
}

However, this causes gaps in the audio.

I was thinking it would be ideal if I could somehow repair these with a ReplaceFrameAvg() function, which takes the average of the frame before and the frame after.

Any ideas?

Gavino · 29th October 2013, 13:49

A simpler solution would be just to use FreezeFrame().

However, your request could be done as follows:

Code:

function ReplaceFrameAvg(clip c, int f) {
  # Note: assumes 0 < f < frameCount-1
  avg = Merge(c.SelectEvery(1,-1), c.SelectEvery(1,1))
  c.Trim(0, -f) + avg.Trim(f, -1) + c.Trim(f+1, 0)
  AudioDub(c) # preserve audio
}

If there are many frames to be replaced, then rather than multiple function calls, it would be more efficient to call Merge() once, do the Trims manually, and do a single AudioDub() after all replacements have been done.

Evil_Burrito · 30th October 2013, 18:21

Yes AviUser, there are hundreds ways to what you want. As Gavino mentioned freezeframe is one method. You could also delete the bad frame, then duplicate the previous one. If you don't want to spend so much time manually checking frames, you could use a temporal denoiser. Or even better, you could use a motion compensated temporal denoiser. Or you could learn how to use the DeScratch/DeSpot filters in combination with DePanEstimate (or mvtools). Although DeScratch/DeSpot results may vary because the settings can be difficult to configure.

AviUser · 31st October 2013, 17:06

Thank you everyone for your help!
This solves my problem.

AviUser · 9th November 2013, 23:01

Just to let you know the results when I applied your tips to a real video:
1. ReplaceFrameAvg() is the best, except causes ghost-like effects when there is movement and doesn't work when there are horizontal lines in two consecutive frames
2. I prefer FreezeFrame() over DeleteFrame2() because no audio blips will be introduced and it won't really increase the size of the video (identical frames compress well)

29th October 2013, 03:01	#1 \| Link
AviUser Registered User Join Date: Mar 2009 Posts: 39	VHS Horizontal Lines: ReplaceFrameAvg() Hello, [Similar topic with no solution] So I have a video sourced from VHS tape recorded in a TV studio. Every minute or so, for 1-5 frames, horizontal white lines appear on the clip and distort the image in those places. What I have been doing is DeleteFrame() on each of these, until I realized that this does not sync audio, so I defined: Code: function DeleteFrame2(clip clp, int framenumber) { return clp.trim(0,framenumber-1) + clp.trim(framenumber+1,0) } However, this causes gaps in the audio. I was thinking it would be ideal if I could somehow repair these with a ReplaceFrameAvg() function, which takes the average of the frame before and the frame after. Any ideas?

29th October 2013, 13:49	#2 \| Link
Gavino Avisynth language lover Join Date: Dec 2007 Location: Spain Posts: 3,431	A simpler solution would be just to use FreezeFrame(). However, your request could be done as follows: Code: function ReplaceFrameAvg(clip c, int f) { # Note: assumes 0 < f < frameCount-1 avg = Merge(c.SelectEvery(1,-1), c.SelectEvery(1,1)) c.Trim(0, -f) + avg.Trim(f, -1) + c.Trim(f+1, 0) AudioDub(c) # preserve audio } If there are many frames to be replaced, then rather than multiple function calls, it would be more efficient to call Merge() once, do the Trims manually, and do a single AudioDub() after all replacements have been done. __________________ GScript and GRunT - complex Avisynth scripting made easier

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30th October 2013, 18:21	#3 \| Link
Evil_Burrito Registered User Join Date: Feb 2013 Posts: 23	Yes AviUser, there are hundreds ways to what you want. As Gavino mentioned freezeframe is one method. You could also delete the bad frame, then duplicate the previous one. If you don't want to spend so much time manually checking frames, you could use a temporal denoiser. Or even better, you could use a motion compensated temporal denoiser. Or you could learn how to use the DeScratch/DeSpot filters in combination with DePanEstimate (or mvtools). Although DeScratch/DeSpot results may vary because the settings can be difficult to configure.

31st October 2013, 17:06	#4 \| Link
AviUser Registered User Join Date: Mar 2009 Posts: 39	Thank you everyone for your help! This solves my problem.

9th November 2013, 23:01	#5 \| Link
AviUser Registered User Join Date: Mar 2009 Posts: 39	Just to let you know the results when I applied your tips to a real video: 1. ReplaceFrameAvg() is the best, except causes ghost-like effects when there is movement and doesn't work when there are horizontal lines in two consecutive frames 2. I prefer FreezeFrame() over DeleteFrame2() because no audio blips will be introduced and it won't really increase the size of the video (identical frames compress well)